In general, a production line of a vehicle body includes a welding process. When a plate such as a vehicle body panel is welded, a weldment is applied into a space between electrodes with pressure and current so that a pressed portion is fused by electric resistance heating of a contact portion.
In order to satisfy increasing demand of assembly quality of a vehicle body, welding quality needs to be improved. However, it is difficult to guarantee the welding quality solely by monitoring a welding machine. Therefore, ultrasonic testing is representatively used for checking the welding quality after the vehicle body is welded.
FIG. 1 is a cross-sectional view of a conventional welded portion quality determining system using ultrasonic waves. The conventional welded portion quality determining system includes an ultrasonic wave generator 100, a housing 110, a medium 120, and a layer 130.
In the ultrasonic testing for testing welding quality of a resistance point according to the related art, a liquid transmission medium is coated on a surface of an object to be tested. Since intensity of ultrasonic waves with respect to a time axis is represented as a pulse type graph in the ultrasonic testing result, the graph may not be easily comprehended with basic knowledge.
One with comprehensive reading technology manually brings an ultrasonic probe into contact with a surface of a welded portion coated with the liquid medium and reads the graph to determine quality of the welded portion.
As described above, due to the manual processes of coating the liquid medium and reading the graph, it is difficult to quantify the test result of the welding quality of the welded portion of the vehicle body using the conventional ultrasonic testing, and it is difficult to correctly test the welding quality.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.